Protein synthesis

Protein synthesis

grade 12

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revise

• •What is a DNA molecule? –

  •is a molecule that contains the biological instructions that make each species unique.

  •Nucleotide consists of a phosphate group, deoxyribose sugar and nitrogenous base (Adenine, Thymine, Guanine, Cytocine).

  •DNA carries the genetic code for protein synthesis.

  •What is RNA?

  •nucleic acid made up of nucleotides, it differs from DNA in that it contains Uracil instead of Thymine.

  •What are the three types of RNA?

  •mRNA carries the code for protein synthesis from DNA to ribosome

  •rRNA forms ribosomes.

  • tRNA brings amino acids to the ribosome for protein synthesis.

Briefly explain the process of DNA replication

• •The process during which a DNA molecule makes an exact copy of itself.

  •The double helix unwinds,

  •The weak hydrogen bonds between nitrogenous bases break and two DNA unzip to separate.

  •Each original DNA strands now serves as a template on which the complement is built, by attaching complementary nitrogenous bases to the original two DNA strands.

  •The two newly formed identical DNA molecule consists of one original strand and one new strand.

Open Ended

1. What is the function of a DNA?

2. What is the difference between RNA and DNA?

Protein synthesis

• •The process by which proteins are made in each cell of an organism to form enzymes, hormones and new structures of cells. 

• •Various amino acids present in the cytoplasm are linked to form proteins.

  •There are 20 different amino acids and are combined at a large variety.

  •The type of protein that is formed is determined by the number of amino acids and the sequence of amino acids.

  
  

• •Proteins generally contains 300 or more amino acids, the smallest proteins contains 50 amino acids.

  •Base triplets are three consecutive nitrogenous bases on the DNA

  •They determine which amino acids is to be placed in the protein and the sequence in which the protein is to be placed.

  •Protein synthesis occurs in two stages.

1. Transcription

• •Occurs in the nucleus.

  •A section of DNA double helix unwinds, resulting in:

  •The weak hydrogen bonds between nitrogenous bases breaking,

  •The DNA unzips in this particular section of the DNA

  •One strand acts as a template, which is used to form a complementary strand messenger RNA (mRNA)

  •This is done using free RNA nucleotides in the nucleoplasm

  •The mRNA now contains the code for the protein that is to be formed.

• •Codons are three adjacent nitrogenous bases on mRNA and they code for a particular amino acid .

  •The mRNA will now move out of the nucleus through a nuclear pore into the cytoplasm, where it attaches to the ribosome.

Codon of bases on mRNA

Open Ended

The following is a sequence of base triplets in DNA: GAA - GTA - TTT - AAA

(a) If guanine, found in the first base triplet, is removed, explain how this would affect the structure of the protein. (2)

(b) Name the process that occurs when the sequence of bases in DNA changes. (1)

Translation

• •Occurs in the cytoplasm

  •The tRNA in the cytoplasm has three adjacent nitrogenous bases called anti-codon, each of which codes for a specific amino acids.

  •The mRNA codon will be complementary to the tRNA anti-codon

  •tRNA brings the required amino acids to the ribosome according to the codons on mRNA

  •A peptide bond will link the amino acids together to form the required protein.

Open Ended

why do you think is protein synthesis important

answer

• Process to produce specific proteins required for cells, antibodies, blood, enzymes and hormones 

• Proteins are reserve energy source in the body

•  Nucleoproteins present in the chromosomes are important for cell division and heredity